Block-based motion estimation method

Abstract

A motion estimation method for determining a resultant motion vector. The motion estimation method includes: performing a first searching operation starting from an initial motion vector to determine an intermediate motion vector, wherein the first searching operation is performed according to a first searching principle; and performing a second searching operation starting from the intermediate motion vector, to determine the resultant motion vector, wherein the second searching operation is performed according to a second searching principle. The first searching operation is a rough search, while the second searching operation is a fine search.

What is claimed is:  
     
       1. A motion estimation method for determining a resultant motion vector, the motion estimation method comprising:
 using an initial motion vector for performing a first searching operation according to a first searching principle, so as to determine an intermediate motion vector by a video processor, wherein the first searching operation is performed when a variation of motion vectors surrounding a current block is more than a predefined threshold, the first operation being performed by: (1) determining a main direction; (2) searching in the main direction according to a central block to determine a block having a minimum cost function value; (3) using the block having the minimum cost function value as the central block; and (4) searching in a direction orthogonal to the main direction according to the central block obtained in step (3) to determine a block having the minimum cost function value; and 
 using the intermediate motion vector for performing a second searching operation according to a second searching principle, so as to determine the resultant motion vector by the video processor. 
 
     
     
       2. The motion estimation method of  claim 1 , wherein the first searching operation is a rough search. 
     
     
       3. The motion estimation method of  claim 1 , wherein the first searching principle comprises:
 selecting one of two searching directions as an initial searching direction for the first searching operation. 
 
     
     
       4. The motion estimation method of  claim 3 , wherein the two searching directions are orthogonal. 
     
     
       5. The motion estimation method of  claim 3 , wherein the first searching principle comprises:
 performing the first searching operation according to each of the two searching directions alternately. 
 
     
     
       6. The motion estimation method of  claim 1 , wherein the second searching operation is a fine search. 
     
     
       7. The motion estimation method of  claim 1 , wherein the second searching principle comprises:
 performing the second searching operation according to a predetermined pattern. 
 
     
     
       8. The motion estimation method of  claim 7 , wherein the predetermined pattern is a small diamond pattern. 
     
     
       9. The motion estimation method of  claim 7 , wherein the predetermined pattern is a large diamond pattern. 
     
     
       10. A motion estimation method for determining a first motion vector, the motion estimation method comprising:
 selecting, by a video processor, a main direction as an initial searching direction; 
 when a variation of motion vectors surrounding a current block is more than a predefined threshold, performing, by the video processor, a first searching operation on a plurality of blocks according to the initial searching direction with respect to a central block, so as to determine a first block having a minimum cost function value; 
 using the block having the minimum cost function value as the central block and performing, by the video processor, a second searching operation on a plurality of blocks in a second direction according to the central block that is orthogonal to the main direction, so as to determine a second block having a minimum cost function value in the second direction; and 
 if the first block and the second block correspond to an identical block, setting, by the video processor, a motion vector corresponding to the identical block as the first motion vector. 
 
     
     
       11. The motion estimation method of  claim 10 , wherein at least one of the first and second searching operation comprises:
 calculating a cost function value according to each searched block. 
 
     
     
       12. The motion estimation method of  claim 11 , wherein the cost function value is a sum of absolute differences. 
     
     
       13. The motion estimation method of  claim 10 , wherein the main direction is determined according to a variance value corresponding to a plurality of motion vectors.